The concept of a central tire inflation system (CTIS) for vehicles is well-known. A central tire inflation system allows the operator to control the air pressure of the tires for improved performance of the tires and of the vehicle. However, the central tire inflation systems currently available suffer from two primary drawbacks. First, the axle and hub and possibly other parts must be extensively modified in order to accommodate a conventional system. Second, no separate central tire inflation systems are currently available for trailers of tractor-trailer rigs. The present invention satisfies this long-felt need by providing a central tire inflation system and further is designed to be applicable to both trailers as well as other vehicles and further that requires no modification to existing axle tubes or hubs.
Central tire inflation systems in general are an important feature. Specifically, an off-road vehicle will often drive on soft, muddy surfaces and then switch to harder surfaces, such as paved roads. To obtain proper traction on soft, muddy surfaces, the tire should be operated at a relatively low pressure. To obtain proper traction and optimal fuel mileage on harder surfaces, the tires should be operated at relatively high pressures.
The differences between preferred high tire pressures (hard surfaces) and preferred low tire pressures (soft surfaces) may be quite large. For example, some truck tire manufacturers recommend a maximum tire pressure of 120 psi for highway conditions and 8 to 15 psi for extremely soft conditions such as sand, mud and swamps. A tire pressure for intermediate road conditions may be approximately 40 psi. Of course, in the case of trailers, the preferred tire pressure will also be dependent upon the weight of the goods or equipment carried in the trailer.
Another reason justifying the employment of central tire inflation systems is road surface deterioration. It is known that over-inflated tires are a major cause of road surface deterioration. Road repair and road building have become increasingly expensive and it is therefore foreseeable that governmental entities may begin penalizing the operators of trucks and tractor-trailers for operating equipment on public roads with improperly inflated tires or over-inflated tires.
Of course, another reason justifying central tire inflation systems is fuel economy. Soft tires on highways reduce gas or fuel mileage. A central tire inflation system that automatically controls the air pressures of trailer tires on a highway will increase fuel efficiency as well as improve road surface longevity.
As noted above, central tire inflation systems in general are well-known and kits for retrofitting existing equipment to accommodate central tire inflation systems are also known. However, the presently available systems and kits require extensive design changes and/or modifications to existing equipment in order to accommodate the systems. This problem could be overcome by providing a central tire inflation system that would simply screw on to or otherwise readily attach onto the ends of axles and readily attach onto the hubs.